Copper-containing aluminum casting alloys such as A355 and A206 has proven difficult to cast after degassing with a non-reactive gas such as N2 or Ar. Compared to gaseous chlorine degassing the castings tend to have poor mechanical properties and visible surface defects. The use of chlorine gas in molten metal processing is to be minimized due to its negative impact on the environment. This project is focused on understanding the mechanism during degassing with N2 or Ar that gives rise to poor properties. This is a fundamental project to establish the root cause of the problem and to recommend a green and clean method to process Cu-containing Al alloys during molten stage.